The present invention relates to electromagnetic recording apparatus and more particularly to carrier structures for positioning electromagnetic read/write heads with respect to moving magnetic media such as magnetic tape or discs. In particular the invention relates to a read/write head carrier structure capable of micro-positioning heads relative to magnetic media to facilitate use of high-density data storage formats.
In several related patent applications I have disclosed techniques for fabricating and producing a new generation of electromagnetic read/write heads capable of utilizing high-density data storage and retrieval formats for magnetic media such as flexible tape or discs. Descriptions of several of my read/write head structures are found in the following patent applications: Ser. No. 07/294,351, filed Jan. 9, 1989, entitled ELECTROMAGNETIC READ/WRITE HEAD, now U.S. Pat. No. 4,984,118; Ser. No. 531,832 filed Jan. 1, 1990, now U.S. Pat. No. 5,122,917, entitled READ-WRITE HEAD ARRAY FOR MAGNETIC MEDIA; and Ser. No. 531,881, filed Jan. 1, 1990, entitled ELECTROMAGNETIC READ/WRITE HEAD WITH ANTI-SIDE-WRITING READ/WRITE GAP. Because my read/write heads are both small and closely spaced, they permit narrower data tracks to be laid down on magnetic media and subsequently retrieved. Data tracks approximately 1- to 11/2-mils in width are readily achievable using arrays of my heads, allowing for data track densities of from 600-800 tracks per inch. Current formats used on 31/2-inch flexible discs provide track densities of approximately 135 tracks per inch. My proposed high-density format will thus greatly increase the storage capacity of magnetic media.
One enduring problem associated with higher-density media formats is the precision required to position the electromagnetic read/write heads, relative to the adjacent media. Presently-used data formats employ tracks 7-8 mils in width in part to help insure accurate tracking. Relatively wide tracks (7-8 mils) insure a high level of repeatability, allowing individual tracks to be accessed in spite of variations in the dimensions of different media samples, different tolerances and settings when media is transferred from drive to drive and media expansion and contraction due to temperature and humidity.
Accurate, repeatable tracking of significantly narrower data tracks has challenged designers and manufacturers. Consequently, there is a need for a new type of electromagnetic read/write head carrier structure which can make use of a new generation of high-density head arrays to provide a 5- to 7-fold increase in storage densities on magnetic media.
Accordingly, it is an object of the present invention to provide a carrier for a magnetic media read/write head structure which employs conventional head positioning devices, such as those used with current disc drives, for macro-positioning of the heads, and incorporates an additional micro-positioning device on each servo arm to enable the heads to precisely track narrower data tracks for use in higher-density formats.
It is a further object of the invention to provide a means for micro-position adjustment of heads on a servo arm using heads which are supported on a separate subframe mounted in a floating, friction-free condition on the servo arm.
Accordingly, a carrier structure is provided for read/write head structures comprising a first movable subframe, such as an arm, adapted for macro-position adjustment. The carrier structure also includes a second movable subframe for micro-position adjustment, the second movable subframe being mounted in a floating, friction-free condition on the first subframe and structured to carry directly the read/write head structure. And a motor means is provided which is drivingly interposed between the first and second subframes for adjusting the position of the second subframe with respect to the first subframe.
In a preferred embodiment, the second movable subframe is in the form of a head carriage or support platform on which a read/write head structure is mounted. The floating, friction-free mounting is provided by means of a flexure support extending between the first subframe (servo arm) and the second subframe (head carriage). The flexure support permits limited relative movement between the head carriage and the servo arm along a single axis of movement. The motor means drivingly interposed between the arm and head carriage serves as a micro-positioner for inducing relative movement therebetween. The motor means includes a conductive coil on one of the first or second subframes and one or more permanent magnets on the other subframe. The micro-position of the second subframe/head carriage is determined by the magnitude and direction of current passing through the conductive coil. An embodiment employing a pair of carrier structures for accessing opposite sides of flexible magnetic media such as a disc is also disclosed.